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Effect of cathode/anode area ratio on electrochemical performance of lithium-ion batteries
Son, Bongki,Ryou, Myung-Hyun,Choi, Jaecheol,Kim, Sang-Hern,Ko, Jang Myoun,Lee, Yong Min Elsevier 2013 Journal of Power Sources Vol.243 No.-
<P><B>Abstract</B></P> <P>The effects of cathode/anode area ratio on the electrochemical performance of lithium-ion batteries are investigated using 2032-type coin full cells. As the anode area is increased from 1.13 (ø12 mm) to 2.54 cm<SUP>2</SUP> (ø18 mm) while maintaining the cathode area as 1.13 cm<SUP>2</SUP> (ø12 mm), both coulombic efficiency and discharge capacity at the first formation step become increasingly worse, probably owing to greater formation of solid electrolyte interphase (SEI). Moreover, rate capability also declined with increased anode area, whereas discharge capacity retention behavior during 1C/1C charge/discharge cycling appeared similar except for a slightly decreased capacity of coin cells with larger anode areas. The findings indicate that cathode/anode area ratio should be carefully evaluated to achieve reliable data on electrochemical performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Relatively larger anode causes low initial coulombic efficiency and discharge capacity. </LI> <LI> Rate capability and cycle life are also dependent on cathode/anode area ratio. </LI> <LI> Slightly larger anode area is recommended for better electrochemical properties. </LI> </UL> </P>
Measurement and Analysis of Adhesion Property of Lithium-Ion Battery Electrodes with SAICAS
Son, Bongki,Ryou, Myung-Hyun,Choi, Jaecheol,Lee, Taejoo,Yu, Hyung Kyun,Kim, Jong Hun,Lee, Yong Min American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.1
<P>The adhesion strength of lithium-ion battery (LIB) electrodes consisting of active material, a nanosized electric conductor, and a polymeric binder is measured with a new analysis tool, called the Surface and Interfacial Cutting Analysis System (SAICAS). Compared to the conventional peel test with the same electrode, SAICAS gives higher adhesion strength owing to its elaborate cutting-based measurement system. In addition, the effects on the adhesion property of the polymeric binder type and content, electrode density, and measuring point are also investigated to determine whether SAICAS provides reliable results. The findings confirm SAICAS as an effective and promising tool to measure and analyze the adhesion properties of LIB electrodes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-1/am404580f/production/images/medium/am-2013-04580f_0014.gif'></P>
Choi, Jaecheol,Son, Bongki,Ryou, Myung-Hyun,Kim, Sang Hern,Ko, Jang Myoun,Lee, Yong Min The Korean Electrochemical Society 2013 Journal of electrochemical science and technology Vol.4 No.1
The consequences of electrode density and thickness for electrochemical performance of lithium-ion cells are investigated using 2032-type coin half cells. While the cathode composition is maintained by 90:5:5 (wt.%) with $LiCoO_2$ active material, Super-P electric conductor and polyvinylidene fluoride polymeric binder, its density and thickness are independently controlled to 20, 35, 50 um and 1.5, 2.0, 2.5, 3.0, 3.5 g $cm^{-3}$, respectively, which are based on commercial lithium-ion battery cathode system. As the cathode thickness is increased in all densities, the rate capability and cycle life of lithium-ion cells become significantly worse. On the other hand, even though the cathode density shows similar behavior, its effect is not as high as the thickness in our experimental range. This trend is also investigated by cross-sectional morphology, porosity and electric conductivity of cathodes with different densities and thicknesses. This work suggests that the electrode density and thickness should be chosen properly and mentioned in detail in any kinds of research works.
김도헌(Dohun Kim),신봉기(Bongki Shin),손민(Min Son),구자예(Jaye Koo),강문중(Moonjung Kang),장홍빈(Hongbeen Chang) 한국가시화정보학회 2013 한국가시화정보학회지 Vol.11 No.2
A flow visualization near submerged nozzle of solid rocket motor was conducted by experiments. A numerical simulation was also performed to reveal detailed phenomena. Radial cold flow simulating hot gas was introduced by a porous grain model which was manufactured by perforated steel plates. The grain model was mounted in high-pressure chamber which has quartz glass at the top of the grain model. From the high-speed images, a rotating vortex was observed and the two type of counter-rotating momentums were generated in numerical results. The rotating momentum was generated at the fin-slot grain because of unbalance between high-velocity flow from slots and low-velocity flow from fin-bases. As a result, roll torques can be produced by the rotating vortex tube.
이용민(Yong Min Lee),손봉기(Bongki Son),서명원(Myungwon Seo),이혜원(Hyewon Lee),최재철(Jaecheol Choi),이윤주(Yunju Lee) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Lithium secondary batteries have been widely used for mobile devices as a power source due to their highest energy density among various secondary batteries. Recently, they started to be applied to hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). Comparing to small-sized lithium secondary batteries, largeformat lithium secondary batteries should have different cell chemistry and design for enhanced safety and high power characteristics. LiMn₂O₄ and amorphous carbon are newly used for cathode and anode materials owing to higher safety and performance, respectively. Moreover, the heat-resistive separator should be applied for vehicle application. However, the more important thing is that the electrode coating layer should be manufactured as thin as possible for tens of kW power requirement of HEVs with limited cell number less than 100. The cell reliability is also insured for about 10 years at low and high temperatures (-46~66℃).
Skewed Spray Characteristics of Impinging Injector
Bimal Subedi,Inchul Lee,Min Son,Bongki Shin,Chanwoo Seo,Jaye Koo 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.12
The atomization characteristics of doublet skewed impinging injectors with a like-on-like arrangement was investigated and compared in this paper for various angle of incident and skewness fraction at various Reynolds conditions using water as a simulant. In this study, the liquid sheet formed along with its variance with skewness factor were analysed using the methods of spray image photography. The graphical relationship between factor of skewness with Reynolds number and angle of spray was derived as the result.
Anatomical and Clinical Correlates of Depression and Anxiety After Stroke
SeJoo Kim,YooSun Moon,NakKyung Choi,YoungShin Kim,BongKi Son,SangKyu Lee,DoHoon Kim 대한신경정신의학회 2004 PSYCHIATRY INVESTIGATION Vol.1 No.1
Objectives-The impact of white matter lesions on depressive or anxiety symptoms after stroke has not been fully investigated. This study was undertaken to investigate the clinical and pathoanatomic correlates of depression and anxiety in acute stroke patients, including subcortical lesions (deep white matter, periventricular white matter and subcortical gray matter) Materials and Methods-Sixty-nine patients with acute stoke were recruited. The numbers and volumes of infarcts affecting the different anatomic sites were evaluated in the brain lesions located in regions such as the cortex, brain stem and cerebellum. White matter lesions and subcortical gray matter lesions were rated by Fazekas classification on MRI images. Depressive and anxiety symptoms were rated by Beck depression inventory (BDI) and Beck anxiety inventory (BAI), respectively. Various anatomical and clinical variables were analyzed between depression or anxiety group and the control group (non-depressive or non-anxiety group), in order to evaluate the correlates of depression. Results-There were significant correlations between depression and periventricular hyperintensity and deep white matter hyperintensity in the acute stroke patients. There were no significant pathoanatomic correlations between anxiety and brain lesions. Conclusions-Our findings suggest that periventricular and deep white matter lesions may increase the risk of depression after stroke. However, to draw more definite conclusions, our findings need to be replicated in larger samples.